Interleukin-8 and melanoma growth-stimulating activity (GRO) are induced by ultraviolet B radiation in human keratinocyte cell lines

IL-17 and TNF synergistically modulate cytokine expression while suppressing melanogenesis: potential relevance to psoriasis

Inflammation-associated pigmentation changes are extremely common, but the etiology behind this clinical observation remains elusive. Particularly, it is unclear how the myriad of cytokines known to be involved in inflammatory skin processes affect epidermal melanocytes. We sought to determine how IL-17 and TNF influence normal human melanocytes, as these two cytokines have been implicated in various skin diseases. IL-17 and TNF jointly stimulated broad inductions of cytokines , including melanoma mitogens CXCL1 and IL-8. Moreover, IL-17 and TNF synergistically inhibited pigmentation-related signaling and melanin production, and induced keratinocytes production of β-defensin 3, an antagonist for melanocortin-receptor 1. When analyzing psoriasis lesions that are known to over express IL-17 and TNF, we observed an increase in melanocyte number and a simultaneous decrease in pigmentation signaling. Furthermore, therapeutic neutralization of TNF and IL-17 with mAbs results in a rapid recovery of pigment gene expression in psoriasis lesions. These results demonstrate that IL-17 and TNF can impact both the growth and pigment production of melanocytes, which may contribute to the pigmentation changes associated with psoriasis. These findings may allow the development of novel therapeutics for pigmentary disorders and bring new insights into the immune milieu surrounding melanocytes and related neoplasms.

UVB upregulates the bax promoter in immortalized human keratinocytes via ROS induction of Id3

Id3 belongs to the inhibitor of differentiation family of helix-loop-helix transcription factors, important in proliferation, differentiation and apoptosis. We showed that Id3, but not Id2 or Id1, mediates the UVB-sensitization of immortalized keratinocytes by inducing caspase 9-dependent apoptosis. In this study, quantitative PCR analysis revealed a time-dependent increase in Id3 mRNA induced by UVB, dependent on reactive oxygen species. UVB upregulated promoter activity of Id3, but not Id2, at early time points, as shown by reporter assays and also stabilized Id3 mRNA, increasing its half-life from 10 to approximately 60 min. We next examined downstream events related to UVB-induced Id3 upregulation and investigated the effects of UVB or ectopic expression of Id3 on bax promoter activity. Regulatory elements in the bax promoter that mediate transcriptional activation by UVB and Id3, in the absence of p53, were identified. Bax promoter deletion analysis revealed that transcriptional activation by UVB involves a 738-bp region upstream from the transcription start site of bax. Mimicking the effects of UVB, ectopic expression of Id3 also upregulated bax mRNA and activated this 738-bp fragment. Mutational analysis of the transcription binding sites further showed that point mutations of the E-box region found in the 738-bp fragment, but not in a 174-bp fragment, completely abolished Id3- and UVB-inducible bax promoter activity, thus confirming the importance of Id3 and UVB-mediated Id3 upregulation in activating the bax promoter. These results suggest a mechanism whereby reactive oxygen species upregulation of Id3 relieves repression of bax via E-box-binding factors.

Endogenous phospholipid metabolite containing topical product inhibits ultraviolet light-induced inflammation and DNA damage in human skin

BACKGROUND

N-palmitoylethanolamine (PEA) and organic osmolytes are endogenous components of the human epidermis and are generated from phospholipids in the stratum granulosum. PEA has been shown to exert potent antioxidant and anti-inflammatory activities. The endogenous organic osmolytes such as betaine and sarcosine control skin humidity, but have also been shown to inhibit ultraviolet (UV) light-induced oxidative stress in keratinocytes.

OBJECTIVES

To investigate the effect of a PEA- and organic osmolyte-containing topical product (Physiogel AI) on the development of UV light-induced erythema, thymine dimer formation and p53 tumor suppressor gene activation, as well as intercellular adhesion molecule 1 (ICAM-1) and Ki67 expression in normal human skin.

METHODS

The UV-induced erythema was measured by a spectrofluorometric method. Thymine dimers, p53, ICAM-1 and Ki67 were detected in skin biopsies using immunohistochemistry.

RESULTS

Physiogel AI cream significantly inhibited the development of UV light-induced erythema and thymine dimer formation in normal human skin, but did not alter the number of Ki67+ proliferating keratinocytes and the expression of p53 and ICAM-1.

CONCLUSIONS

Our results suggest that PEA and organic osmolytes might represent a new generation of compounds which suppress UV-induced photodamage.

Microarray analysis of UVB-regulated genes in keratinocytes: downregulation of angiogenesis inhibitor thrombospondin-1

BACKGROUND

Ultraviolet (UV) B light is an environmental mutagen that induces changes in cutaneous gene expression leading to immune suppression and carcinogenesis. Keratinocytes are a primary target for UVB.

OBJECTIVE

To further delineate UVB-induced gene expression changes in keratinocytes.

METHODS

cDNA microarray technology was utilized to examine gene expression in normal human KC (NHKC) following 20 mJcm(-2) UVB irradiation. Data was confirmed by semi-quantitative RT-PCR.

RESULTS

Microarray analysis revealed 57 genes were upregulated, and 27 genes were downregulated, by at least two-fold following UVB. One downregulated gene was the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1). Semi-quantitative RT-PCR confirmed persistent downregulation of TSP-1 up to 18h following UVB. Microarray analysis also revealed upregulation of platelet-derived endothelial cell growth factor (PD-ECGF)--an angiogenesis activator.

CONCLUSION

Our results suggest a gene expression mechanism by which UVB induces an angiogenic switch in keratinocytes. This may represent an important early event promoting neovascularization and growth of cutaneous neoplasms.

Autocrine and paracrine regulation of melanocytes in human skin and in pigmentary disorders

Recently melanogenic paracrine or autocrine cytokine networks have been discovered in vitro between melanocytes and other types of skin cells. These include endothelin (ET)-1, granulocyte macrophage colony stimulating factor, membrane-type stem cell factor (SCF) and growth-related oncogene-alpha for interactions between keratinocytes and melanocytes, and hepatocyte growth factor and soluble type SCF for interactions between fibroblasts and melanocytes. These networks are also associated with corresponding receptors expressed on melanocytes, including ET B receptor and the SCF receptor, c-KIT. Consistent with in vitro findings on the melanogenic paracrine or autocrine cytokine networks, we have found that the up- or down-regulation of such networks is intrinsically involved in vivo in the stimulation of melanocyte functions in several epidermal hyper- or hypo-pigmentary disorders. These are ET-1/ET B receptor as well as membrane type SCF/c-KIT for ultraviolet B-melanosis, granulocyte macrophage colony stimulating factor for ultraviolet A-melanosis, ET-1/ET B receptor as well as membrane type SCF for lentigo senilis, growth related oncogene-alpha for Riehl's melanosis, sphingosylphosphorylcholine for hyperpigmentation in atopic dermatitis, ET-1 for seborrhoeic keratosis, soluble type SCF as well as hepatocyte growth factor for dermatofibroma and café-au-lait macules, and c-KIT for vitiligo vulgaris. These unveiled regulatory mechanisms involved in the abnormal up- or down-regulated levels of lesional melanocyte function provide new insights into therapeutic tools utilizing blockage of responsible cytokine networks.

The primary role in biologic activity of the neutrophil chemokines IL-8 and GRO-alpha in cultured nasal epithelial cells

Primary nasal epithelial cells were investigated for their ability to synthesize and deliver neutrophil chemotactic factors (chemokines) following tumor necrosis factor-alpha (TNF-alpha) induction. The chemokines interleukin8 (IL-8), growth-related oncogene-alpha (GRO-alpha), epithelial cell-derived neutrophil attractant-78 (ENA-78), and granulocyte chemotactic protein-2 (GCP-2) have been detected and characterized and shown to have different potencies in the chemotaxis of neutrophils. Cultures of primary nasal epithelial cells were treated with TNF-alpha in concentrations of 20 and 200 ng/ml for 2, 8, 24, and 72 h. The chemokine protein concentrations in the supernatants of the incubations were determined by the ELISA technique. Chemokine mRNA expression in epithelial cells was also measured using the reverse transcriptase-polymerase chain reaction (RT-PCR). The biologic activity of the chemokines was identified using a three-step high-performance liquid chromatography (HPLC) technique, a bioassay involving measurement of neutrophil chemotaxis in a single Boyden chamber. Both the IL-8 and GRO-alpha proteins and their respective mRNA appear to be induced by TNF-alpha in epithelial cells. The chemotactic responsiveness of both GRO-alpha and IL-8 appears to predominate after 24 h incubation with TNF-alpha. The chemokines GCP-2 and ENA-78 were only weakly induced by TNF-alpha. The neutrophil chemokines IL-8 and GRO-alpha were synthesized in nasal epithelial cell culture induced by TNF-alpha in biologically active concentrations of 0.8 ng/ml and 1.42 ng/ml, respectively. It appears that both the IL-8 and GRO-alpha chemokines may contribute to neutrophil tissue migration in sinusitis, whereas GCP-2 and ENA-78 are of secondary importance to the chemotaxis of neutrophils in this condition.

Analysis of the ultraviolet B response in primary human keratinocytes using oligonucleotide microarrays

UV radiation is the most important environmental skin aggressor, causing cancer and other problems. This paper reports the use of oligonucleotide microarray technology to determine changes in gene expression in human keratinocytes after UVB treatment. Examination of the effects of different doses at different times after irradiation gave a global picture of the keratinocyte response to this type of insult. Five hundred thirty-nine regulated transcripts were found and organized into nine different clusters depending on behavior patterns. Classification of these genes into 23 functional categories revealed that several biological processes are globally affected by UVB. In addition to confirming a majority up-regulation of the transcripts related to the UV-specific inflammatory and stress responses, significant increases were seen in the expression of genes involved in basal transcription, splicing, and translation as well as in the proteasome-mediated degradation category. On the other hand, those transcripts belonging to the metabolism and adhesion categories were strongly downregulated. These results demonstrate the complexity of the transcriptional profile of the UVB response, describe several cellular processes previously not known to be affected by UV irradiation, and serve as a basis for the global characterization of UV-regulated genes and pathways.

Interleukin-8 and human cancer biology

The aggressive nature of metastatic human cancer has been shown to be related to numerous abnormalities in growth factors and their receptors. These perturbations confer a tremendous growth advantage to the malignant cells. Interleukin-8 (IL-8), originally discovered as a chemotactic factor for leukocytes, has recently been shown to contribute to human cancer progression through its potential functions as a mitogenic, angiogenic, and motogenic factor. While it is constitutively detected in human cancer tissues and established cell lines, IL-8 expression is regulated by various tumor microenvironment factors, such as hypoxia, acidosis, nitric oxide, and cell density. Understanding the mechanisms of both inducible and constitutive IL-8 expression will be helpful in designing potential therapeutic strategies of targeting IL-8 to control tumor growth and metastasis. In this review, the role and regulation of IL-8 expression in the growth and metastasis of human cancer with a focus on human pancreatic adenocarcinoma will be discussed.

Regulation of interleukin-8 expression by tumor-associated stress factors

Tumor and host cells frequently express interleukin-8 (IL-8). IL-8 has been shown to be motogenic, mitogenic, and angiogenic and to play important roles in human tumor progression. IL-8 expression can be induced by numerous stress factors present in the tumor environment, such as hypoxia, acidosis, hyperglycemia, hyperosmotic pressure, high cell density, hyperthermia, radiation, and chemotherapeutic agents. Understanding the mechanisms of IL-8 expression and regulation will be helpful in designing potential therapeutic modalities targeting IL-8 to control tumor growth and metastasis.

Papillomavirus type 16 oncogenes downregulate expression of interferon-responsive genes and upregulate proliferation-associated and NF-kappaB-responsive genes in cervical keratinocytes

Infection with high-risk human papillomaviruses (HPV) is a major risk factor for development of cervical cancer. Expression of the HPV E6 and E7 oncoproteins increases in differentiating keratinocytes, resulting in inactivation of the p53 and retinoblastoma proteins, two important transcriptional regulators. We used cDNA microarrays to examine global alterations in gene expression in differentiating cervical keratinocytes after infection with retroviruses encoding HPV type 16 (HPV-16) E6 and E7. Expression of 80 cellular genes (approximately 4% of the genes on the array) was altered reproducibly by E6 and/or E7. Cluster analysis classified these genes into three functional groups: (i) interferon (IFN)-responsive genes, (ii) genes stimulated by NF-kappaB, and (iii) genes regulated in cell cycle progression and DNA synthesis. HPV-16 E6 or a dominant negative p53 protein downregulated multiple IFN-responsive genes. E6 decreased expression of IFN-alpha and -beta, downregulated nuclear STAT-1 protein, and decreased binding of STAT-1 to the IFN-stimulated response element. E7 alone was less effective; however, coexpression of E6 and E7 downregulated IFN-responsive genes more efficiently than E6. The HPV-16 E6 protein also stimulated expression of multiple genes known to be inducible by NF-kappaB and AP-1. E6 enhanced expression of functional components of the NF-kappaB signal pathway, including p50, NIK, and TRAF-interacting protein, and increased binding to NF-kappaB and AP-1 DNA consensus binding sites. Secretion of interleukin-8, RANTES, macrophage inflammatory protein 1alpha, and 10-kappaDa IFN-gamma-inducible protein were increased in differentiating keratinocytes by E6. Thus, high-level expression of the HPV-16 E6 protein in differentiating keratinocytes directly alters expression of genes that influence host resistance to infection and immune function.

Growth-regulated peptide-alpha (GRO-alpha) production by oral keratinocytes: a comparison with skin keratinocytes

Growth regulated peptide (GRO-alpha) is chemotactic for neutrophils. It also stimulates keratinocyte proliferation and migration, and angiogenesis in cutaneous wound healing. We compared GRO-alpha production by normal human skin and oral keratinocytes, and the effects of cytokine stimulation. Resting keratinocytes produced little, if any, GRO-alpha. TNF-alpha induced a large increase in GRO-alpha mRNA and protein production in both cell types (P<0.001). However, the response of oral keratinocytes was significantly higher (P<0.01). Oral, but not skin, keratinocytes also produced significant amounts of GRO-alpha in response to IL-1 alpha (P<0.005) and IL-4 (P<0.01) stimulation. Indeed, there was an additive effect on GRO-alpha production when oral keratinocytes were stimulated with combinations of TNF-alpha and IL-1 alpha or TNF-alpha and IL-4. Neither cell type responded to interferon gamma. Keratinocyte GRO-alpha production may help selectively recruit neutrophils in mucocutaneous inflammatory diseases, and differences in production by skin and oral keratinocyte could explain the different presentation of these diseases at the two sites. The increased GRO-alpha responsiveness of oral keratinocytes may also help explain the excellent wound healing properties of oral mucosa.

Up-regulation of interleukin-1beta-stimulated interleukin-8 in human keratinocytes by nitric oxide

Nitric oxide (NO) is able to regulate the expression of a number of inflammatory mediators. In this study, the effect of NO on the expression of the chemokine interleukin-8 (IL-8) by primary human keratinocytes and the lines KB and HaCaT was examined. Incubation with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) for 24 hr increased IL-8 protein only in HaCaT cells, partly due to the presence of constitutive interleukin-1 (IL-1). However, in combination with IL-1beta, SNAP enhanced both IL-8 mRNA and protein in all three cell types. Transfection of cells with an IL-8 promoter reporter gene construct showed that the effect of NO was at least partly due to transcriptional activation. Despite small variations in the response to NO by the three cell types, these results demonstrate that NO can up-regulate IL-1beta-stimulated IL-8 expression in human keratinocytes. This study provides a regulatory mechanism which may be important in the context of skin inflammation, and supports the role of NO as an inflammatory mediator in the skin.

Purification and characterization of an allergy-induced melanogenic stimulating factor in brownish guinea pig skin

We have demonstrated recently that phenylazonaphthol (PAN) allergy-induced hyperpigmentation in brownish guinea pig skin is associated with the concomitant appearance of a melanogenic soluble factor(s) that activates the intracellular signal transduction system, including phosphatidylinositol turnover subsequent to ligand-receptor binding in cultured guinea pig melanocytes. In this study we have purified and characterized the PAN-induced melanogenic stimulating factor (PIMSF) that occurs in allergy-associated hyperpigmented skin. By successive column chromatography on TSK 2000SW, Mono Q, and octadecyl-NPR, the PIMSF was purified to homogeneity with a single band of apparent molecular mass of 7.9 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific bioactivity of PIMSF increased by 5,195-fold over the original skin homogenate. In cultured guinea pig melanocytes, this purified PIMSF had the potential of activating an intracellular signal transduction system such as inositol 1,4,5-trisphosphate formation and intracellular calcium levels through a pertussis toxin-sensitive G protein-coupled receptor. PIMSF consistently caused a rapid translocation of cytosolic protein kinase C (PKC) to membrane-bound PKC within 5 min of treatment with a return to the basal level after 120 min. The stimulating effects of PIMSF on proliferation and melanization of cultured guinea pig melanocytes were abolished completely by a PKC down-regulating agent (phorbol 12,13-dibutyrate). PIMSF was similar in molecular mass to rat growth-related oncogene alpha (GRO-alpha; molecular mass of 7.9 kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had immunocross-reactivity with GRO-alpha upon Western immune blotting analysis. Further, the stimulatory effect of purified PIMSF on DNA synthesis of cultured guinea pig melanocytes was suppressed markedly by the addition of anti-rat GRO-alpha antibody, implying that the PIMSF is apparently identical to GRO-alpha. These findings suggest that PAN allergy provides a new mechanism of hyperpigmentation in which biological factors such as the GRO-alpha superfamily generated within allergy-induced skin stimulate melanocytes through activation of the PKC-related signal transduction pathway.

Oral keratinocyte immune responses in HIV-associated candidiasis

INTRODUCTION

Candidiasis is the most commonly encountered opportunistic infection among HIV-positive subjects. The purpose of this study was to assess specific keratinocyte immune parameters in the pseudomembranous and erythematous forms of HIV-associated oral candidiasis.

MATERIAL/METHODS

This collaborative study from three centers analyzed 25 HIV-positive and 10 HIV-negative subjects with either pseudomembranous or erythematous candidiasis. Oral biopsy specimens from lesional tissues were procured, and histopathologic features were correlated with immunohistochemical and in situ hybridization investigations for the expression of interleukin 1 alpha, interleukin 8, antimicrobial calprotectin, lymphocyte populations, and Candida antigen.

RESULTS

Both pseudomembranous and erythematous candidiasis among HIV-infected subjects showed a mild interface lymphocytic mucositis with the presence of neutrophilic subcorneal abscesses in the latter. Erythematous candidiasis cases that failed to show surface mycelia, did yield positive results for Candida antigens in the parakeratinized layer. The expression of inflammatory chemokines were positive in all groups and calprotectin appeared to serve as a keratinocyte barrier to hyphal penetration.

CONCLUSIONS

The erythematous form of candidiasis is often devoid of hyphae yet the presence of Candida antigens in the surface epithelium implicates an immune or allergic process. The intactness of chemokines and antimicrobial calprotectin in keratinocytes may explain why disseminated candidiasis is rarely encountered in HIV-infected patients.

A synthetic peptide inhibitor for alpha-chemokines inhibits the growth of melanoma cell lines

Melanoma growth stimulatory activity (MGSA/GROalpha) is a 73 amino acid peptide sharing sequence characteristics with the alpha-chemokine superfamily. MGSA/GROalpha is produced by diverse melanoma cell lines and reported to act as an autocrine growth factor for the cells. We tested the binding of MGSA/GROalpha to melanoma cell lines, Hs 294T and RPMI7951, and found that these cells could bind to MGSA/GROalpha but not to interleukin-8. Recently, we defined a novel hexapeptide, antileukinate, which is a potent inhibitor of binding of alpha-chemokines to their receptors on neutrophils. When antileukinate was added to melanoma cells, it inhibited the binding of MGSA/ GROalpha. The growth of cells from both melanoma cell lines was suppressed completely in the presence of 100 microM peptide. The cell growth inhibition was reversed by the removal of the peptide from the culture media or by the addition of the excess amount of MGSA/GROalpha. The viability of Hs 294T cells in the presence of 100 microM peptide was > 92%. These findings suggest that MGSA/GROalpha is an essential autostimulatory growth factor for melanoma cells and antileukinate inhibits their growth by preventing MGSA/GROalpha from binding to its receptors.

Keratinocytes and cytokine/growth factors

Cytokines are polypeptide growth factors produced by most nucleated cells in the body, including epithelial cells, keratinocytes, and Langerhans cells in the skin. Cytokines can be classified into interleukins, tumor necrosis factors, chemokines, colony-stimulating factor, interferons, and growth factors. Like classic hormones, cytokines bind to specific receptors to transmit their messages to target cells. Cytokine receptors can be divided into three cytokine receptor superfamilies: the immunoglobulin superfamily, the hematopoietin family, and the tumor necrosis factor family. Following cytokine/cytokine-receptor binding (first messenger), a signal transduction pathway is initiated. Factors affecting homeostasis in the skin and oral mucosa include a delicate balance between cytokines/cytokine-receptors and their antagonists. An imbalance in these variables can influence the development of cutaneous and oral diseases-such as lichen planus, autoimmune disorders, and some neoplastic processes- and can affect wound healing. Potential uses of cytokines include cancer and antiviral therapy.